A one in four or one in three canola rotation is still the best way to manage blackleg. A one in two year rotation, no matter how one manipulates it, is higher risk.
For example, available evidence does not support that a crop sequence of canola-canola-wheat-wheat is better than canola-wheat-canola-wheat. Latest research indicates that blackleg severity tends to be highest for canola on canola stubble, then lower with one year between canola crops, and lower still with two and three years between canola crops. We know based on crop insurance records and a recent Agriculture and Agri-Food Canada study that canola on canola yields lower than canola on any other stubble.
When growing canola on a one in two year rotation, consider rotating varieties on those fields. Many genes are responsible for blackleg resistance in canola and at least 16 described virulent blackleg races are currently found on the Prairies. Growers don’t know which varieties have which resistance genes, but rotating varieties will likely bring a mix of resistance genes to the field over time. This reduces the risk of selecting for blackleg races that can overcome the specific genetic resistance in any one variety. Click here for more blackleg management tips.
Published on March 9, 2011